I am firmly in the “key UI elements should be visible” camp. I also agree that Apple violates that rule occasionally.
However, I think they do a decent job at resisting it in general, and specifically I disagree that removing the home button constitutes hiding an UI element. I see it as a change in interaction, after which the gesture is no longer “press” but “swipe” and the UI element is not a button but edge of the screen itself. It is debatable whether it is intuitive or better in general, but I personally think it is rather similar to double-clicking an icon to launch an app, or right-clicking to invoke a context menu: neither have any visual cues, both are used all the time for some pretty key functions, but as soon as it becomes an intuition it does not add friction.
You may say Apple is way too liberal in forcing new intuitions like that, and I would agree in some cases (like address bar drag on Safari!), but would disagree in case of the home button (they went with it and they firmly stuck with it, and they kept around a model with the button for a few more years until 2025).
Regarding explaining the lack of home button: on iOS, there is an accessibility feature that puts on your screen a small draggable circle, which when pressed displays a configurable selection of shortcuts—with text labels—including the home button and a bunch of other pretty useful switches. Believe it or not, I know people who kept this circle around specifically when hardware home button was a thing, because they did not want to wear out the only thing they saw as a moving part!